1. Field of the Invention
The present invention relates generally to an injection molding apparatus and, in particular, to a front mountable nozzle that delivers melt to a number of mold cavities spaced around the nozzle.
2. Related Art
Edge gating from a nozzle of an injection molding apparatus through a number of edge gate seals is well known. A multi-cavity edge, or side, gated injection molding apparatus 100 is shown in FIG. 1 as described in U.S. Pat. No. 5,494,433 to Gellert, issued Feb. 27, 1996, which is incorporated in its entirety herein by reference thereto. Generally, the multi-cavity edge-gated injection molding apparatus 100 includes several nozzles 102, one of which is shown in FIG. 1, that are coupled to a manifold 118 to receive a melt stream of moldable material therefrom. Each nozzle 102 is mounted in a cylindrical opening 104 in a mold 106 to convey pressurized melt through a nozzle melt channel 108 to mold gates 110, which lead to mold cavities 112 in mold 106. Mold cavities 112 are spaced radially around nozzle 102. Each mold gate 110 extends through a gate insert 114, which is held in position by a gate insert retainer plate 122. Each mold gate 110 is aligned with a gate seal 116 that is threadably coupled to nozzle 102. As such, the location of gate seals 116 is generally fixed relative to the mold 106.
As illustrated in FIG. 1, manifold 118 is a “floating” manifold, which is positioned below a back plate 120 and coupled to mold 106 through nozzle 102. This arrangement allows for thermal expansion of manifold 118 and nozzle 102 in an axial direction. In such an arrangement, requisite axial thermal expansion is accommodated by having a sliding/telescopic arrangement between a sprue bushing 124 fixed to a mold back plate 120 and manifold 118. However, axial thermal expansion of nozzle 102 is restricted in a direction of the mold cavity by the relatively fixed position of gate seals 116. Consequently, gate seals 116 bear the load of both the manifold and the edge-gating nozzle during operation of the injection molding apparatus. Due to the strenuous and repetitive nature of the injection molding process, such a load condition may cause misalignment of the gate seals with their respective mold gates and excessive wear of the gate seals resulting in leakage and more frequent repair and maintenance. In order to access gate seals 116 for repair or maintenance purposes, edge-gated systems often require that the entire system be advanced forward or removed.
As such there exists a need in the injection molding industry for an injection molding apparatus that maintains alignment of a plurality of gate seals with a plurality of respective mold gates and that reduces the load on the gate seals during operation and facilitates access for maintenance.